THE PHOTOSYNTHETIC LIGHT DISPENSATION SYSTEM - APPLICATION TO MICROPHYTOBENTHIC PRIMARY PRODUCTION MEASUREMENTS

Measurements of microphytobenthos primary production were carried out in the German Wadden Sea in order to test the application of a 'Photos ynthetic Light Dispensation System', which was originally developed fo r photosynthetic research of higher plants. A description of the compu ter-controlled system, consisting mainly of a subunit providing the ir radiance (photosynthetically active radiation, PAR), and a subunit equ ipped with a Clark-type electrode for measuring oxygen production and respiration processes is given. The system allows rapid and reproducib le measurements of photosynthesis-irradiance (P-E) curves at light mod es predetermined by the computer and simple, rapid data analysis. Addi tionally, P-E curves obtained by this system were compared to those re ceived by simultaneously conducted C-14 measurements. Primary producti on measured by the oxygen method was on average 2.00 times higher than the values obtained by the 14C method. Production rates varied betwee n 1.7 and 4.1 mg C mg chl a(-1) h(-1) with a mean of 2.75 mg C mg chl a(-1) h(-1).